The use of portable electronic products having various functions as well as small size and low weight has been rapidly increased due to the development of electrical and electronic technologies. A battery is generally used as a power supply for the operation of the portable electronic products, wherein rechargeable secondary batteries are mainly being used.
Such secondary batteries have received attention as a new energy source for improving environmental friendliness and energy efficiency because the secondary batteries not only have a primary advantage of capable of significantly reducing the use of fossil fuels but also byproducts according to the use of energy are definitely not generated. A secondary battery includes an electrode assembly including a cathode, an anode, and a separator which is disposed between the cathode and anode and insulates the cathode and the anode.